A battery pre-doping method uses lithium carbonate to reduce lithium loss during the first cycle and increase energy density and cycle life.
Asahi Kasei has developed a pre-doping technology that uses lithium carbonate as an additional lithium source for high-voltage lithium-ion batteries (LIBs) with silicon-based anodes. The technology is designed to reduce the irreversible capacity loss that occurs during the first charge-discharge cycle of silicon-rich batteries, potentially increasing energy density and extending battery life.
The development comes as demand grows for higher-energy-density batteries for electric vehicles (EVs) and humanoid robots. Battery makers are increasingly replacing part of the graphite in anodes with silicon-based materials and raising the operating voltage of cathode materials. Silicon can store more lithium than graphite, but silicon-based anodes also experience significant irreversible capacity loss during the first charge. This reduces the amount of lithium available for subsequent cycles and limits both battery life and energy density.
One way to compensate for this loss is to add more cathode active material, but that increases material consumption and battery costs. Asahi Kasei instead focused on lithium carbonate, a relatively low-cost material already used in LIBs.
The challenge has been that lithium carbonate normally decomposes at a voltage well above the operating range of conventional LIBs, making it difficult to use as a pre-doping material. Asahi Kasei’s technology addresses this issue by adding specific electrolyte additives that promote the decomposition of lithium carbonate at typical LIB operating voltages.
Under this approach, lithium carbonate is added to the cathode as a sacrificial lithium source. During the initial charging process, it decomposes and supplies additional lithium to compensate for the lithium consumed by the silicon-based anode.
In internal testing, an NMC (nickel-manganese-cobalt) cell with an anode containing 90% graphite and 10% silicon monoxide (SiO) achieved a 10% increase in energy density using the technology.
Asahi Kasei says the approach can also improve cycle life while keeping the cost per watt-hour low. It can be incorporated without major changes to existing battery manufacturing lines and could be used with various combinations of cathode and anode materials. The company plans to license the technology and offer flexible collaboration models based on each customer’s development stage.
